Magnetic particle hyperthermia: Neel relaxation in magnetic nanoparticles under circularly polarized field

TL;DR

This paper analyzes how Neel relaxation affects heat generation in magnetic nanoparticles under different polarization fields, providing exact solutions to optimize hyperthermia treatment efficiency.

Contribution

It offers exact analytical solutions for magnetization dynamics in nanoparticles under circular and linear polarization, highlighting frequency-dependent heat dissipation mechanisms.

Findings

Linear polarization is more effective below Larmor frequency.

Circular polarization yields higher losses above Larmor frequency.

Provides a theoretical framework for optimizing hyperthermia treatments.

Abstract

The mechanism of magnetization reversal in single-domain ferromagnetic particles is of interest in many applications, in most of which losses must be minimized. In cancer therapy by hyperthermia the opposite requirement prevails: the specific loss power should be maximized. Of the mechanisms of dissipation, here we study the effect of Neel relaxation on magnetic nanoparticles unable to move or rotate and compare the losses in linearly and circularly polarized field. We present exact analytical solutions of the Landau-Lifshitz equation as derived from the Gilbert equation and use the calculated time-dependent magnetizations to find the energy loss per cycle. In frequencies lower than the Larmor frequency linear polarization is found to be the better source of heat power, at high frequencies (beyond the Larmor frequency) circular polarization is preferable.